The invention relates to a cryomagnet system, in particular for use with nuclear magnetic resonance (NMR) experiments or ion cyclotron resonance (ICR) experiments, with a low-loss helium cryostat comprising a helium container and one or a plurality of tubes with thin walls for the suspension the helium container and the feed or exit of helium into or out of the helium container, respectively, the tubes being sealed to the atmosphere outside the helium container by at least one non-return low-pressure valve.
Such a cryomagnet system is for example known from the German Patent 31 53 405.
Nowadays, in particular cryomagnet systems for NMR spectrometry are cooled by extremely low-loss helium cryostats which have a loss-rate of the liquid helium of only 10 ml/h and below. Yet with such a low-loss cryostat of conventional construction the actually observed losses of helium are higher than the ones theoretically calculated, because at these low-loss rates even loss sources which could normally be neglected become already noticeable.
Another problem with the mentioned conventional cryomagnet systems are disturbances of the magnetic field generated at the locus of the sample to be examined, said disturbances obviously arise within the cryomagnet system. Whereas external disturbing influences such as electromagnetic interference fields as well as forced mechanical vibrations of the system can be shielded and/or compensated by means of extensive measures, disturbing side bands and/or broadening of the lines in the NMR signals can still be observed which are only due to internal disturbing influences.
Therefore it is an object of the present invention to provide a cryomagnet system in which the losses of helium are reduced to the theoretical limit and at the same time internal perturbations of the magnetic field generated at the locus of the sample are minimized to a great extend.
This object is solved by the present invention in that at least one exhaust pipeline is provided with a device for dissipating the energy of the expanding helium.